Need Explanations; like equations on a paper or here. Question 1) An iron railro

Question

Need Explanations; like equations on a paper or here.

Question 1)
An iron railroad track 1000 feet long is at a temperature of 0 oC. How much does it expand when heated to 33 oC?
Use the coefficient of linear expansion 12 x 10-6 / oC given in Table 5.2 of the text.
a) .04 feet b) .08 feet c) .4 feet d) .8 feet e) 4 feet

Question 2)
An aluminum airplane wing is 30 meters long when its temperature is 20 oC. At approximately what temperature will it be 5 centimeters (.05 meters) shorter? Use the linear coefficient of expansion for aluminum, 25 x 10-6 / oC given in Table 5.2 of the text and pick the closest answer from the choices.

a) 40 oC b) 0 oC c)

Explanation / Answer

1) dl = alfa*L*dT = 12*10^-6*1000*33 = 0.4 feet

2) dl = alfa*L*dT

dt = -0.05/(25*10^-6*30) = -66.67

t2-t1 = -66.67

t2-20 = -66.67
t2 = -46.67

3) dQ = dU + dW

140 = dU +100

dU = 40J


4) dQ = m*c*dT = 2*390*(220-20)= 150kJ

5) dQ = m*c*dT = 3*4180*(20-3) = 213kJ

6) dQ = m*c*dT = 1*890*(660-20) = 580 kJ

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